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| United States Patent |
6,054,375
|
|
Quick
|
April 25, 2000
|
Method for making laser synthesized ceramic electronic devices and
circuits
Abstract
Laser apparatus and methods are provided for synthesizing areas of ceramic
substrates or thin films, such ceramics as Silicon Carbide and Aluminum
Nitride, to produce electronic devices and circuits as integral electron
circuit components thereof. Circuit components such as conductive tabs,
interconnects, wiring patterns, resistors, capacitors, insulating layers
and semiconductors are synthesized on the surfaces and within the body of
such ceramics. Selected groupings and arrangements of these electronic
circuit components within the substrates or thin films provide a wide
range of circuits for applications such as digital logic elements and
circuits, transistors, sensors for measurements and monitoring effects of
chemical and/or physical reactions and interactions of materials, gases,
devices or circuits that may utilize sensors. The electronic elements and
components offer the advantages of providing thermal compatibilities with
the substrate, since they are an integral part thereof and consequently
are compatible therewith regarding thermal coefficients of expansion and
thermal dissipation.
| Inventors:
|
Quick; Nathaniel R. (894 Silverado Ct., Lake Mary, FL 32746)
|
| Appl. No.:
|
088046 |
| Filed:
|
June 1, 1998 |
| Current U.S. Class: |
438/535; 257/E21.134; 257/E21.592; 257/E21.596; 438/513 |
| Intern'l Class: |
H01L 021/26; H01L 021/42 |
| Field of Search: |
438/535,510,513,550,542,104,931,932,960
428/402,409-410,698-699,701-704
427/96,126.2,227,555
|
References Cited
U.S. Patent Documents
| 5145741 | Sep., 1992 | Quick | 428/402.
|
| 5391841 | Feb., 1995 | Quick | 174/258.
|
| 5733609 | Mar., 1998 | Wang | 427/561.
|
Primary Examiner: Bowers; Charles
Assistant Examiner: Thompson; Craig
Attorney, Agent or Firm: Holland, Jr.; Clay
Parent Case Text
This is a CONTINUATION-IN-PART of application Ser. No. 08/759,235 filed
Dec. 5, 1996, now U.S. Pat. No. 5,887,607 entitled LASER SYNTHESIZED
CERAMIC ELECTRONIC DEVICES AND CIRCUITS (as Amended), Inventor Nathaniel
R. Quick, which is still pending as of this filing.
Claims
What is claimed as new is:
1. A method for making a transistor device by laser synthesis directly onto
a monolithic substrate of essentially a crystalline or polycrystalline
ceramic compound, said method comprising, the steps of:
a. providing a monolithic ceramic compound substrate having a reverse side
and of essentially n-type semiconductive carriers responsive to laser
synthesis conversion;
b. converting a first section of said substrate to a p-type semiconductive
carrier by laser synthesis;
c. converting a second section of said substrate to a p-type semiconductive
carrier by laser synthesis spaced apart from said first p-type carrier
section, to thereby form a separation therebetween;
d. inscribing on said substrate by laser synthesis a first conductor
connected to said first p-type section and a second conductor connected to
said second p-type section, to provide electrical connections to said
p-type sections on said substrate; and
e. inscribing on said reverse side of said substrate a third conductor,
said conductors providing means for connecting said device to other and
external components, elements and circuits, and to thereby provide a p-n-p
type semiconductor transistor.
2. A method for making a transistor device of claim 1, which includes the
steps of placing said p-n-p transistor in a hermetically sealed chamber
having a laser beam transmission window therein, and forming a first
dielectric layer on a surface of said substrate disposed between said
spaced apart p-type carrier sections and a second conductor layer on top
of said dielectric layer by means of laser synthesis and various selected
metallo-organic gases introduced into said chamber, and said laser beam is
directed into said chamber through said chamber window for producing said
dielectric and conductor layers on said device, to thereby produce a
(p-n-p)-type channel transistor.
3. A method for making a transistor device of claim 2, in which said laser
is of a type selected from the group consisting of Nd:YAG, frequency
doubled Nd:YAG or Excimer lasers, said substrate is a ceramic compound of
a material selected from the group consisting of Aluminum Nitride, Silicon
Carbide or Boron Nitride and said gases are selected from the group
consisting of phosphate gas, di-borane gas, tungsten hexafloride gas,
titanium tetra chloride gas, titanium ethoxide gas, aluminum sec-butoxide
gas silane gas and tetra carbonyl nickel gas.
4. A method for making a plurality of electrical components and elements
individually or in a circuit arrangement on a film essentially of a
crystalline or polycrystalline ceramic compound in a metallo-organic
containing atmosphere, said method comprising, the steps of:
a. providing a vapor deposition chamber and system for depositing selected
films on a support substrate contained therein;
b. depositing a film of a crystalline or polycrystalline ceramic on a
support substrate contained in said chamber by vapor deposition
techniques;
c. providing a plurality of metallo-organic dopants containing gas/vapor
for use in said chamber at selected processing steps to thereby cause
chemical changes in selected areas of said film; and
d. directing a focused laser beam onto a surface portion of said film
disposed in said chamber and causing relative motion between said beam and
film so as to laser synthesize a plurality of electronic devices, circuit
elements and interconnecting wiring leads thereon to thereby form circuits
on said substrate.
5. A method of claim 4, in which said components and elements include a
plurality of devices such as electronic sensors, diodes, transistors and
conductors.
6. A method of claim 4, in which said laser is of a type selected from the
group consisting of Nd:YAG, frequency doubled Nd:YAG or Excimer lasers,
and said film is a ceramic compound of a material selected from the group
consisting of Aluminum Nitride, Silicon Carbide or Boron Nitride.
7. A method of claim 4, in which said metallo-organic dopants are selected
from the group including di-borane, silane, phosphine, titanium tetra
chloride, titanium ethoxide, aluminum sec-butoxide, tetra carbonyl,
tungsten hexafluride and nitrogen.
8. A method of claim 4, in which successive film layers are stacked on one
another each having devices and circuitry formed on each layer to produce
a multi-layer three dimension integrated circuit structure.
9. A method of claim 4, in which said conductors inscribed on said
substrate may be connected to electrical conductors external to said
substrate by means of molten metal or molten metal alloys for bonding.
10. A method of claim 4, in which said conductors inscribed on said
substrate may be electrically conductive pads, tabs, vias and
interconnecting wiring leads.
Description
The present invention relates to and is concerned with the creation of
electronic devices and circuits as integral electronic circuitry that are
synthesized on the surfaces and within the body of bulk and thin films of
selected ceramic materials by means of laser writing and processing
thereon with selected laser devices in an air and/or selected atmosphere.
BACKGROUND
Certain ceramics, such as Silicon carbide (SiC) Boron Nitride (BN) and
Aluminum Nitride (AlN), are known to exhibit electrical properties ranging
from insulating to semiconducting to conducting, as discussed in U.S. Pat.
No. 5,145,741, issued Sep. 8, 1992, entitled "Converting Ceramic Materials
to Electrical Conductors and Semiconductors", and U.S. Pat. No. 5,391,841,
issued Feb. 21, 1995, entitled "Laser Processed Coatings on Electronic
Circuit Substrates", both issued to Nathaniel R. Quick. The ceramics under
consideration herein, are used to create devices such as conductive tabs,
interconnects, vias, wiring patterns, resistors, capacitors, semiconductor
devices and the like electronic components by laser synthesis on the
surfaces and within the body of such ceramics to thereby eliminate
photolithography processes which require numerous steps and generate
undesirable chemical pollutants when processing such traditional
electronic devices, components and circuitry.
As is well known Alumina (Al.sub.2 O.sub.3) dominates the dielectric market
as an integrating substrate or device carrier in electronics packaging.
AlN, BN and SiC are also of interest, due to their Thermal Coefficient of
Expansion (TCE) and for their dielectric constant and higher thermal
conductivity than that of Al.sub.2 O.sub.3. These properties are of
substantial interest for new high temperature and aggressive environment
applications, particularly where high integrated circuit packing densities
are required. In the prior art, metallization methods, including dry-film
imaging and screen printing have been used for the production of
conductive patterns on Alumina, however, metal compatibility with the
newer high thermal conductivity ceramic materials such as AlN, BN and SiC,
have not been completely solved. Copper and silver paste exhibit a TCE
mismatch aggravated by high temperatures and are subject to oxidation
which increases their resistivity. In particular, bonding of copper to AlN
has proved to be nontrivial. Alumina or stoichiometric aluminum oxynitride
(AlON) coatings must be developed on the AlN surface through passivation
processes. These passivation processes have poor reproducibility,
especially when hot pressed AlN substrates are used. Thus, the direct
laser synthesis of conductors in AlN, BN and SiC substrates appears to
provide solutions to this long standing prior art problem with regard to
metallization and for more simple processing techniques for creating
devices and circuitry that are compatible with selected ceramic
substrates, while satisfying the need for higher temperature, aggressive
environment, and higher density integrated circuit packaging applications.
SUMMARY OF THE INVENTION
The present invention provides for the use of selected ceramic materials,
chemical doping of the ceramic materials, and use of laser synthesis
processing techniques applied to selected areas of the ceramic body for
creating electronic component devices individually and in an
interconnected circuit arrangement on the surface of and/or within a
substrate body of the ceramic material, such as for examples AlN, BN and
SiC, whether the ceramic is thin film or bulk material. The invention
uniquely utilizes the properties of the doped ceramic in combination with
selected laser synthesis techniques to create a variety of electronic
devices and components, such as capacitors; resistors; diodes;
transistors; logic and digital devices; electrical conductors, connection
tabs conductive holes or vias through substrates; and various types of
sensors. More specifically, by selective chemically doping designated
surface areas and layers of the ceramic substrate body or film with
chemical elements, a ceramic is produced that may be readily converted in
designated areas thereof by laser synthesis, using one of several laser
devices, to create discrete electronic devices and electronic circuit
arrangements. The creation of these various electronic devices and
circuits takes place incrementally, such as making a (p-n)-type carrier
semiconducting device by laser synthesizing two adjacent areas, one for
the (p) and the other for the (n) portion. The required electrical
conductive tab connections are laser synthesized on either side of the p-n
junction, to thereby form a p-n junction diode. The formation of a simple
(p-n-p) or (n-p-n) arrangement is accomplished by an added step in the
above diode process by adding an additional (p) or (n) laser synthesized
component, with the appropriate electrical conductor connections as noted
above with respect to the diode example. Such elemental electronic devices
are readily produced by simple laser synthesis without the traditional
multiple step processing and attendant pollution and environmental
contamination problems of the prior art processes.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention can be described in more detail and understood with
the assistance of the accompanying drawings wherein:
FIG. 1, shows an arrangement for practicing certain aspects of the
invention, illustrating several electrical or electronic elements on a
substrate that have been produced thereon by laser synthesis processing;
FIGS. 2-5, depict several arrangements of electronic components and
elements produced on various substrates in accordance with the teachings
of the present invention, illustrating how readily such elements may be
disposed with respect to each other, to thereby create the various devices
in accordance with the present inventive teachings;
FIG. 6, depicts a p-n junction device produced in a substrate body or film
with appropriate electrical conductive leads, such device may be used as a
diode;
FIG. 7, depicts an n-p-n transistor device produced in accordance with the
present invention;
FIG. 8, depicts an n-channel transistor that is produced in accordance with
the teachings of the present invention, illustrating the versatility and
uniqueness of the invention; and
FIG. 9, depicts an air-tight chamber and laser arrangement utilized to
perform certain processing steps in accordance with the invention, for
producing chemical doping of entire selected ceramic substrate bodies or
films and or selected areas thereof; and for selective dielectric and/or
conductive coatings.
Such processing techniques are well known in the prior art, but are used
herein in accordance with the teachings of the invention to produce unique
devices and circuitry utilizing fewer and simpler steps than required in
the prior art and to eliminate many of the prior art contamination and
environmental problems associated therewith.
DETAILED DESCRIPTION OF THE INVENTION
The present invention focuses on the processes and materials utilized to
produce circuit components such as electronic elements, components,
devices and circuit interconnection insitu on monolithic ceramic compound
substrate or body or of a film thereof, deposited on a support substrate.
These circuit components are formed by direct conversion of selected areas
of the substrate or film by laser synthesis, producing conductor,
semiconductor and insulative areas insitu thereon.
Referring now to the drawings, there is shown in FIG. 1, an arrangement for
practicing the present invention, including a laser system 10 consisting
of a laser device 12 and a laser beam focussing lens 14. A focussed laser
beam 16 is shown impinging upon a monolithic substrate 18 of a crystalline
or polycrystalline ceramic compound material having a rectangular
configuration. The top surface of substrate 18 is designated by reference
20, and has an area 22 depicted thereon that has been converted to a
semiconductor material by laser beam 16 with a small circular hole or via
24 intersecting therewith that extends through substrate 18 from
semiconductor 22 by laser drilling and conversion, to a surface 25 on the
reverse side of substrate 18 where it terminates in a conductive
connection. The terminal ends and inner exposed surface of via 24 has been
converted to an electroconductor material by laser beam 16 as it drills
through substrate 18 between surface 22 and 25. On the reverse side of
substrate 18 on surface 25 there is depicted an area on surface 25 that
has been converted to an conductor pad 26 that is formed by laser beam 16,
which is connected to conductor via 24, where it terminates at surface 25.
A conductor pad 26 has been formed on surface 25 by rotating substrate 18
so that surface 25 is exposed to direct laser beam 16 interaction for
direct conversion of pad 26 to a conductor material in accordance with the
teachings of the present invention. Continuing with the description of
FIG. 1, there is shown a conductor strip 30 connected to an edge of
semiconductor area 22 on surface 20 and extending therefrom to the edge of
substrate 18 and thence along a substrate surface 32 and thence along
surface 25, terminating thereon with an electroconductor tab 28. Both
conductors 30 and tab 28 have been produced by direct laser beam 16
conversion.
Referring now to FIGS. 2-4, there is shown a plurality of substrates that
have had certain sections thereof converted directly into elements and
components of electronic devices by laser beam synthesis in accordance
with the teachings of the present invention. Shown in FIG. 2, is a
monolithic substrate 41 of crystalline or polycrystalline ceramic compound
material that is responsive to conversion by laser beam 16 exposure. More
specifically, substrate 41 and a main body thereof may be a crystalline or
polycrystalline ceramic compound material from the group including
Aluminum Nitride (AlN), Silicon Carbide (SiC) or Boron Nitride (BN), for
examples, as disclosed in U.S. Pat. No. 5,145,741, dated Sep. 8, 1992,
issued to applicant, the foregoing materials are known to be convertible
directly by laser beam inscription, from insulative to semiconductive to
resistive and to conductive materials. However, applicant knows of no
prior art that has utilized such technology to produce devices such as,
sensors, diodes, transistors and circuitry containing such devices insitu
on selected monolithic ceramic substrates as taught by the present
invention. As can readily be appreciated the present invention provides
simpler processes, with fewer processing steps, fewer pieces of processing
equipment and a reduction, if not the elimination, of environmental
pollants and contaminants heretofore associated with the prior art to
produce such devices, as diodes, transistors, sensors and the like, as
examples.
Referring again to FIG. 2, substrate body 40 is depicted as an insulative
crystalline or polycrystalline ceramic compound material, such as AlN, SiC
and BN, as examples. A resistor section 42 is formed on substrate body 40,
having a resistive value in the range of 10.sup.-2 -10.sup.-6 ohm-cm, a
pair of electrical conductors 44 and 46 are formed on substrate 40,
disposed on opposite sides of and connected to resistor section 42, to
thereby produce a resistor insitu on substrate body 40. Another electrical
conductor 48 is formed on the reverse side 50 of substrate body 40. As
shown a portion of substrate body 40, designated 52 and delineated by a
broken line 52, is disposed between electrical conductors 46 and 48, to
form a capacitor.
Referring now to FIG. 3, there is shown a crystalline or polycrystalline
ceramic compound substrate 56, of SiC, chemically doped with aluminum (Al)
forming a p-type carrier (electron holes) semiconductor material. By laser
beam synthesis, conductor 58 is formed on a surface 60 of substrate 56,
and an n-type carrier (electrons) semiconductor 62 is formed at a surface
64 of substrate 56 by laser beam chemical doping with phosphorus (P), and
an electroconductor 66 is formed on a reverse side 64 of substrate 56 and
is electrically connected to n-type carrier 62.
The foregoing formed device is capable of operating as a diode in an
external circuit by connecting conductors 58 and 66 to external leads 68
and 70, respectively, or as a insitu diode when connected to other
components which may be formed on substrate 56 and connected to terminals
58 and 66.
Referring to FIG. 4, there is shown a device 76, that may operate as
various types of sensors, such as thermoresistive, piezoresistive or
chemoresistive, depending the electroresistive properties of a ceramic
compound substrate body 78. There are reverse surfaces 80 and 82 on
substrate body 78, that have conductors 84 and 86 formed on surfaces 80
and 82, respectively, to which external conductor terminals 88 and 90
respectively are provided for external connections.
It should be noted that devices of the type shown in FIG. 4, operate
primarily on the principal of change in resisitivty (ohm-cm) of the laser
beam synthesized ceramic, and therefore, are uniquely adaptable to hostile
environmental operations, such as with automobile and aircraft engines
that are made of ceramic components. As examples, the temperature,
physical changes or distortion and the presence of chemicals occurring in
or near an engine, can be monitored at selected sections of the engines by
depositing a film of crystalline or polycrystalline ceramic compound,
directly onto the engine body at selected sections and subsequently laser
beam synthesizing such films to produce a thermoresistive, piezoresistive
or chemoresistive device from the deposited films. Alternately, the
surface of ceramic engine components comprised of may be made of AlN, SiC
or BN can be directly converted to these types of sensors. Also there are
situations where the engine may have a component part made of ceramic, and
it may be desirable to monitor such component and therefore, the sensors
of the present invention may be disposed thereon and used to monitor such
components. Such devices would consist of resistive areas disposed between
a pair of laser synthesized electroconductor tabs, where the tabs are used
for external connections. It has been experimentally determined that
crystalline or polycrystalline ceramic compounds, such as (AlN), (SiC) and
(BN), may be deposited upon ceramic materials of which automotive and
aircraft engines are made, by means of known vapor or thermal spray
deposition techniques, without debonding therebetween when operating at
elevated temperatures of such engines. Thus, such selectively disposed
devices can be used for remote monitoring of the changes in the engines
readily and simply on a real time basis, when compared with the prior art
techniques. It should be noted that these sensor devices may be
characterized as passive or active devices, that is, when an electrical
bias is applied the device they are active and without the bias they are
passive.
The device depicted in FIG. 5, illustrates one of several arrangements for
elements for a transistor type device. There is shown a crystalline or
polycrystalline ceramic substrate 90 of p-type carrier material designated
92 that has a n-type carrier section laser beam synthesized on reverse
sides of the substrate designated 94 and 96. Over of these n-type carriers
are conductors 98 and 100, respectively formed by laser synthesis on each
layer of n-type carrier sections 94 and 96. On a surface of substrate
section 92 there is formed by laser synthesis a conductor 102. Conductors
98 and 100 each have terminal conductors 104 and 106, respectively
connected thereto for external connections. The device just described may
be utilized as a traditional transistor connected to external circuits or
as an insitu device on a monolithic substrate as part of a circuit
thereon.
In FIG. 6, there is shown an alternate arrangement for a diode, similar to
that shown in FIG. 3 where a substrate body 57 is a crystalline or
polycrystalline ceramic material that is responsive to laser conversion
and it has had p-type carrier and n-type carrier adjacent sections formed
thereon by laser synthesis This arrangement is the traditional
configuration for junction diodes known in the prior art, and may be part
of an external circuit or as a device of an insitu circuit that may be
formed on a monolithic substrate in accordance with of the present
invention.
Referring to FIG. 7, there is shown a (p-n-p)-type transistor having a
configuration different from the (n-p-n)-type transistor shown in FIG. 5.
As shown there is depicted a n-type substrate 150 with two p-type carrier
sections 152 and 154 separated from one another, each p-type sections has
a conductor 162 and 164 connected, respectively thereto and an conductor
160 disposed on a reverse surface of substrate 150. A conductor 162 is
connected to conductor 156 that function as a drain terminal of the
device, while a conductor 164 is connected to conductor 158 that function
as a source terminal of the device. A conductor 166 is attached to
conductor 160 that is also connected to conductor 164 the source terminal
The resultant device is characterized as a traditional (p-n-p)-type
transistor.
FIG. 8, shows a device similar to the device shown in FIG. 7, with the
addition of a dielectric layer 165 formed on the surface of substrate 150
and disposed between p-type carriers 152 and 158. Deposited on top of
dielectric layer 165 is a conductor layer 167 to which a conductive lead
169 is attached for external connections as a gate terminal for the
device. The resulting device is characterized as a n-type carrier channel
transistor.
Referring now to FIG. 9, there is shown a processing arrangement including
laser 12, focussing lens 14 and laser focused beam 16, such as that shown
in FIG. 1 and it operates in a similar manner. Also shown is a chamber
170, including an airtight laser beam transmission window 172 disposed for
transmitting beam 16 therethrough into the chamber. Chamber 170 has an
inlet and valve combination 174 and outlet and valve combination 176
connected to the side wall of the chamber, for injecting and removing
gases into and therefrom, respectively. The chamber is dispose on a
support member 178 forming an airtight seal therewith. Also shown in FIG.
9, there is a substrate 180 upon which a dielectric layer 165 is formed
and a conductive layer 167 is deposited on top of dielectric layer 165.
Substrate 180 is a material such as substrate 150 shown in FIGS. 7 and 8.
The arrangement shown in FIG. 9, is used to convert or add to the surface
of substrates placed therein. As shown, dielectric layer 165 and conductor
167 are of the type shown in FIG. 8 so as to complete the formation of an
n-type carrier channel transistor.
EXAMPLE
To accomplish the unique results derived from the teachings of the present
invention, it is necessary to consider some of the detail processing steps
and procedures thereof. In various sections of the disclosure and claims
the phrases "laser synthesis" and "laser synthesized" have been used to
broadly mean or define, the use of a selected laser beam impinging
(inscribing or writing or drilling) onto or into the body of a crystalline
or polycrystalline substrate or body to thereby cause rapid thermal
heating for melting and the rapid cooling for solidification in selected
exposed areas, causing chemical and physical changes to occur to the
substrate areas exposed to the laser beam. Such exposure to the laser beam
may be accompanied by the use of gases, such as air, oxygen or other
gas/vapor mixtures, that may be a co-operant in the process for causing
such changes. Use of these phrases is consistent with the teachings of
U.S. Pat. Nos. 5,145,741 and 5,391,841, noted herein and both issued to
applicant.
Continuing with the disclosure of the present invention, attention is
directed to the various laser devices used to perform laser synthesis as
envisioned herein. The Table I entitled "Typical Laser Types", setforth
below, list three (3) laser types which have been found satisfactory for
practicing the present invention. A second Table II entitled "Laser
Processing Parameters", shown below discloses eight (8) parameters for
each of the three (3), sample laser types, namely, Nd:YAG, Frequency
Double Nd:YAG and Excimer lasers, that are useful for laser synthesis
processes. These lasers are capable of laser synthesis and/or conversion
of insulating and semiconducting crystalline or polycrystalline ceramics
and to material combinations necessary to fabricate and produce the
various electronic devices and circuits taught by the invention.
The parameters shown have been diligently arrived at after extensive test
and evaluation, and have been selectively used to produce the various
devices and circuits in accordance with the teachings of the present
invention and claims.
TABLE I
______________________________________
Typical Laser Types
SiC SiC
Laser Types Untreated Resistivity Converted Resistivity
Nd:YAG Ohm-cm Ohm-cm
______________________________________
Wavelength: 1064 nm
10.sup.11 5.1 .times. 10.sup.-3
Excimer
Wavelength: 248 nm 10.sup.11 1.2 .times. 10.sup.-3
Frequecy Double 10.sup.11 1.9 .times. 10.sup.-3
Nd:YAG
Wavelength: 532 nm
______________________________________
TABLE II
______________________________________
Laser Processing Parameters
______________________________________
Beam
Pulse energy Diameter Energy density Pulse Duration
Laser Type (J) (cm) (J/cm.sup.2) (nsec)
______________________________________
Nd:YAG 0.0081 0.025 12.5 70
1064 nm
KrF Excimer 0.0034 0.085 2.2 30
248 nm
Nd:YAG 0.0011 0.002 339.5 100
532 nm
______________________________________
Peak Pulse Scan Conversion
Intensity Velocity Energy
(W/cm) (cm/sec) Passes (J/cm.sup.3)
______________________________________
Nd:YAG 1.8 .times. 10.sup.8 0.3 2 1.2 .times. 10.sup.9
1064 nm
KrF Excimer 7.3 .times. 10.sup.7 0.053 1 1.4 .times.
10.sup.9
248 nm
Nd:YAG 3.4 .times. 10.sup.9 2 1 1.67 .times. 10.sup.9
532 nm 2 2 3.35
.times. 10.sup.9
40 1 8.35 .times. 10.sup.7
40 2 1.67 .times. 10.sup.8
______________________________________
The ceramic materials taught by the present invention may be of a
crystalline or polycrystalline structure and are representative of several
hundred possible types from which to choose. For example, Silicon Carbide,
in the Beta-SiC(Zincblende structure) or 6H-SiC (6 bilayers along the
hexagonal crystal direction) are only two of many types of material
structures SiC can have as a convertible ceramic. Similarly, many
structural types exist for laser convertibility, including SiC, AlN and BN
which have been the focus of the disclosure and teaching in accordance
with the present invention. However, it is understood that these ceramics,
may be considered preferred among others which may be selected As can be
appreciated by those skilled in this art, the practice of the present
invention is strongly influenced by a working knowledge of material
science and the unique properties of crystalline or polycrystalline
ceramic materials known in the field of such science. Consequently,
teachings herein are directed toward known factors derived from extensive
experimental and proven results within such science.
Continuing, the selected ceramics, as examples, namely, SiC, AlN and BN
have been used to readily change their initial electrical properties by
"chemical doping" as by means of laser synthesis or conversion. For
example, doping of Beta-SiC ceramic material with phosphorous generates
n-type carrier (electrons), and with aluminum generates p-type carrier
(holes) semiconductive materials. Shown herein below is Table III entitled
"Dopants and Materials Generated by Laser Synthesis". As shown in Table
III, materials such as, SiC and AlN as examples, may be laser synthesized
with dopants, as examples, shown to produce the resultant materials. As
shown, the dopants may be in the form of gases, and the chemical doping
therefrom may be accomplished by the use of a system arrangement
illustrated in FIG. 9 hereof. The process for doping within chamber 70 of
FIG. 9, occurs by laser beam 16 illuminating the selected areas of a
substrate body by inscribing or writing thereon, while simultaneously
causing a gas therein to chemically disassociate and diffuse into the
laser exposed areas of the substrate body to thereby cause chemical,
electrical and physical changes in the properties of the substrate body
where the laser has selectively scribed.
TABLE III
__________________________________________________________________________
DOPANTS AND MATERIALS GENERATED BY LASER SYNTHESIS
RESULTANT MATERIALS
RESULTANT MATERIALS
DOPANT SOURCE DOPANT (No Oxygen Present) (No Oxygen Present)
__________________________________________________________________________
Aluminum Nitride
Silicon Carbide
Di-Borane Boron Boron Boron (p-type)
Boron Nitride (s) Boron Carbide (i)
Aluminum Boride
Silane Silicon Silicon(s) Silicon(s)
Silicon Nitride (i) Silicon carbides(s)
Phosphine Phosphorous Phosphorous Phosphorous (n-type)
Aluminum-Phosphide(s) Boron
Titanium tetra chloride Titanium
Titanium (c) Titanium (s)
Titanium ethoxide Titanium nitride (c) Titanium Silicide(s)
Titanium-Aluminide (c) Titanium Carbide(s)
Aluminum sec-butoxide Aluminum Aluminum Aluminum (p-type)
Aluminum Nitride(s) Aluminum
Carbide
Tetra carbonyl Nickel Nickel Nickel (c)
Nickel Nickel Aluminide (c) Nickel Carbide
Nickel Silicide
Tungsten hexafluoride Tungsten Tungsten Tungsten(c)
Tungsten Nitride Tungsten-Carbide (c)
Tungsten
Nitrogen Nitrogen Nitrogen (n-type) Nitrogen
__________________________________________________________________________
The dopants and resultant materials shown in Table III are illustrative of
many combinations which could be selected within the scope of the
teachings of the present invention.
From the foregoing discussions of Tables I-III, it can readily be
appreciated that devices and circuits of the type taught and claimed
herein can be produced by the appropriate selection of crystalline or
polycrystalline ceramic material; selection of an appropriate type of
laser; operating the laser with appropriate parameters; and using
appropriate dopants.
Until now, the disclosure primarily has discussed the formation of the
devices and circuits on substrate bodies, suggesting that the substrates
are in a non-film structure. However, it is understood that the substrates
envisioned by the invention includes film structures of appropriate
thickness to accommodate the formation of the devices and circuits in
accordance with the teachings hereof. More particularly, the substrates
44, 56, 75, 90 and 150 depicted in the various figures may be substrate
films. Various crystalline or polycrystalline ceramic materials having
properties substantially identical as those of substrates 44, 56, 76, 90
and 150, and others may be readily formed on a support or carrier
substrate through the use of a laser synthesis and chamber depicted in
FIG. 9, for example, by means of known vapor deposition techniques.
Once a layer of film has been formed on a support substrate it may be
processed in a similar manner as the substrates depicted in FIGS. 1-8, in
accordance with the teachings of the invention to produce devices and
integrated circuits. Successive film layers may be formed and processed to
produce a multi-layer structure, that represents a unique feature for
using films, to create a three dimensional structure. Conductive
interconnections between selected layers, devices and circuits may be made
by use of conductive vias such a via 24 depicted in and discussed in
connection with FIG. 1
The present disclosure has herein above emphasized the electrical
properties of various devices, components and circuits that may be
produced, however, it should be noted that another equally important and
unique property or feature of the electrical conductive tab, pads, vias
and interconnection wiring leads, that they are all connectable to or
bondable to traditional external electrical circuits by means of molten
metals or metal alloys to which they are readily bonded More specifically,
the various electrical conductive tabs, pads, vias, and interconnection
wiring leads, whether on a bulk or film material substrate may be brazed
or soldered to external electrical conductors by use of suitable molten
metals and metal alloys. The metal bonding features and properties of the
tabs, pads, vias and wiring leads or conductors are produced as a result
of direct laser scribing, writing etc. as taught by the present invention.
Since this bondable feature of these laser inscribed electrical conductors
are an integral part of the ceramic substrate, the molten bonding may be
performed at higher than traditional brazing or soldering temperatures to
thereby produce high temperature bonding. This higher bonding temperature
will enable the components devices and circuits etc. to operate at higher
temperatures without debonding. In addition, since these devices are an
insitu part of the substrate that support them, heat is more readily
dissipated therefrom owing to the better dielectric constants and higher
thermal conductivity of the ceramics of the present invention than those
of Al.sub.2 O.sub.3 or other prior art substrates.
The foregoing disclosure and teachings of the present invention readily and
adequately demonstrate that direct laser synthesis and chemical process
doping of selected ceramic substrate and film materials, can be utilized
to create and produce electronic devices and circuits uniquely within the
body of such ceramic materials and in which the Thermal Coefficient of
Expansion (TCE) between the devices and circuits are compatible with the
substrate of films owing to their inherent relationship as part of the
starting material and noting that nothing during the processing of the
system has changed their inherent compatibility with respect to TCE
between the substrate and the circuits and devices formed thereon. In
addition to the enhanced TCE properties, the present invention provides
electron devices and circuit arrangements within the selected ceramic
materials that have better dielectric constant and higher thermal
conductivity properties than those of Al.sub.2 O.sub.3 which is
traditionally used as support substrates for electronic devices and
circuits of the type addressed by the present invention.
It is to be understood that the above described embodiments and teachings
of the present invention are only illustrative of the principles
applicable. Various other arrangements and processing modifications may be
envisioned or refined by those skilled in the art without departing from
the spirit and scope of the invention. For example, other ceramic
materials of hexagonal crystalline structure with certain nitride or
carbide compounds, may be adapted to have similar or equivalent processing
properties as disclosed herein, and it is inferred that like electrical
semiconductive, conductive and insulative properties may be attainable
within the spirit and scope of the present invention. Consequently, it is
understood that the present invention is limited only by the spirit and
scope of the disclosure and appended claims.
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